Rear diff Dodge Cummins Amsoil 75W90 15000 miles

[D-Roc]

Here is a sample from my 2006 Dodge Cummins. Have an aftermarket diff cover which allows for a larger fluid capacity (up to 8 quarts as opposed to 4).
Amsoil Severe Gear 75W90
My only question is the presence of water at 0.1%...this doesn't seem high to me, but I'm unfamiliar with how much water is actually acceptable before damage can occur. Last year my rear end went in for bearings at about 140 000 miles....
Sample WAS taken after truck was sitting for an hour or two, so that could explain the 0.1% water...


Na 6
K 1
Si 4
Al 1
Fe 88
Cr 0
Pb 0
Cu 0
Sn 0
Ni 0
Ag 0
Ti 0.13
V 0
Zn 26
Ma 1
Ca 11
B 0
Mo 42
P 1033.8
V100 14.9
V40 100.4
Water T 0.1%


ISO 23/17
5uM 51285
10uM 11853
15uM 766
20uM 14
30uM 71
50uM 3
75uM 1
100uM 0

 

[Johnny]

That sample looks good. Does Dodge recommend 75W-90 or 75W-140? What cover do you have on the diff? I helped a friend install a Mag Hytech on his Ford this past weekend.

 

[DieselTech]

yeah it looks good. We put 140 in all of the dodge rear diffs we do. Mag hytech and PML make great covers

 

[D-Roc]

Originally Posted By: Johnny
That sample looks good. Does Dodge recommend 75W-90 or 75W-140? What cover do you have on the diff? I helped a friend install a Mag Hytech on his Ford this past weekend.


Dodge recommends 75W90 for my year, but I've often wondered if 75W140 will drop my wear any...I may try a change of that next.
Yeah Johnny, Mag-Hytec. I really like them due to the ease of maintenance, and the dipstick.

 

[D-Roc]

Oh, and I also sampled the front diff, but it would be a waste of time posting it in this section...with my free spin/lockout hub kit I have on the truck, the oil looks more like virgin!

 

[DieselTech]

Originally Posted By: D-Roc
Oh, and I also sampled the front diff, but it would be a waste of time posting it in this section...with my free spin/lockout hub kit I have on the truck, the oil looks more like virgin!

LOL now thats funny. Try 75-140 Doc I think it will help.

 

[Jim Allen]

Originally Posted By: D-Roc
Dodge recommends 75W90 for my year, but I've often wondered if 75W140 will drop my wear any...I may try a change of that next.
Yeah Johnny, Mag-Hytec. I really like them due to the ease of maintenance, and the dipstick.


I kinda doubt a 140 will drop the wear any unless you do a lot of towing or were running the 90 grade into high temps often. HOWEVER, since you have such a good run on the 90, and will likely have another, it would be interesting to see if there were any changes.

I just reverted from a 140 syn to a mineral 90 (after installing a limited slip), which I will run for a break in period. The LS manufacturer recommends ONLY a mineral oil with their limited slip... not for wear but to maintain the designed bias ratio. Interestingly, the mineral 90 (a Chevron 80W90) they installed produced slightly lower oil temps on the order of about 10 degrees versus the syn RP 75W140. I observed and recorded diff temps on the drive up to the manufacturer to get the diff installed and then on the return trip.10 degree drop even though the day was considerably warmer for the trip home.

Haven't decided if I will go with a syn or a mineral replacement, but it will be a grade 90. Thus far, no matter what I've done, my diff oil temp has never exceeded 200F so I see no point in a super-thick oil, except to reduce my fuel economy ( ;< ). I have a Mag-Hytec cover, which likely accounts for the lower temps. My "formula" is to run a lighter oil diff if possible and keep it cool. That way, I can have low rolling resistance but with protection from overheating the oil when towing.

I will likely try some syn 75W90 and see if I can notice any apparent drop in biasing capability with the LSD.

 

[D-Roc]

Good points, Jim...one thing to keep in mind is that the Chevron 80W90 (most likely ESI) is a boron based lubricant (says so in the PDF), and is advertised by Chevron to lower operating temps...If I could run it year round, I would. But I need cold temp operation.
Do you know if it was the ESI?

 

[Jim Allen]

Originally Posted By: D-Roc
Good points, Jim...one thing to keep in mind is that the Chevron 80W90 (most likely ESI) is a boron based lubricant (says so in the PDF), and is advertised by Chevron to lower operating temps...If I could run it year round, I would. But I need cold temp operation.
Do you know if it was the ESI?


Not ESI. It's the RPM Universal 80W90, which was formerly the Texaco Multigear EP80W90. I'll run it a few thousand miles for break-in then decide if I will try a syn or go to a better mineral.

 

[D-Roc]

Originally Posted By: Jim Allen
Originally Posted By: D-Roc
Good points, Jim...one thing to keep in mind is that the Chevron 80W90 (most likely ESI) is a boron based lubricant (says so in the PDF), and is advertised by Chevron to lower operating temps...If I could run it year round, I would. But I need cold temp operation.
Do you know if it was the ESI?


Not ESI. It's the RPM Universal 80W90, which was formerly the Texaco Multigear EP80W90. I'll run it a few thousand miles for break-in then decide if I will try a syn or go to a better mineral.



Oh and one more thing, Jim...hope you don't mind I cleverly appropriated your sig for an example to use for my own...gotta give credit where it's due.

 

[Jim Allen]

Imitation is flattery after all!